


Fill your heart up with love

by mrxsm



Category: Marvel Cinematic Universe, Thor (Movies)
Genre: Alternate Universe - College/University, Alternate Universe - Human, Christmas Eve, Christmas Fluff, Clothed Sex, Coming In Pants, F/M, First Time, Grinch References, Nipple Play, Sibling Incest, Trans Female Character, Trans Male Character
Language: English
Status: Completed
Published: 2018-12-04
Updated: 2018-12-04
Packaged: 2019-09-06 17:15:50
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,453
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16836949
Author URL: https://archiveofourown.org/users/mrxsm/pseuds/mrxsm
Summary: Thor and Loki visit their family for Christmas. Thor's hand accidentally visits his sister's chest.





	Fill your heart up with love

Loki wouldn't so much as make eye contact with him. _What was her problem?_ The first time they'd seen each other all year and she was too busy moving Christmas dinner around her plate to even acknowledge his presence. Her hair was growing out now. It reached just below her shoulders and every so often she’d bite the corner of her lip and tuck it back behind her ear when it fell out. Thor had hoped that with everything that had changed over the past twelve months, this unspoken thing between them would too.

They’d always been close when they were younger. It wasn't until Loki started high school too that she’d started to object to Thor hugging her, wrapping his arm around her shoulders, around her waist - the little touches that more than once had them mistaken for a couple by someone they didn’t know. They'd blushed and laughed it off at the time and Thor hadn't thought anything more if it. It was just how they were. Until it wasn't. By the time they graduated they found themselves at different schools in different states and that was that. They’d never had any shared interests except for each other, so maybe growing apart was inevitable.

Thor wasn’t sure how to go about addressing it. He’d hoped that coming home would be an opportunity to start afresh, but Loki was just as stubborn and impossible to understand as ever. From across the table, he heard Frigga sigh at her clipped, one word answers. If his sister had a life at all now she was at college, she wasn’t about to be forthcoming about it.

Never one for polite conversation, their father grunted, clearing his throat. Thor stiffened, the air instantly felt thick and heavy around him. 

“Thor, I’m sure _you’ve_ made some friends this year.” The implication wasn’t lost on any of them.

Uneasy, Thor knew he couldn't respond in a way that didn’t make Loki feel worse, so he mumbled out a “yeah,” knowing it wasn’t what their father wanted either. Story of his life. Lips tightening into a grimace, he slowly mopped up the last of his gravy, trying not to look up. Loki might actually be onto something here.

"Children," Frigga implored, sending a pleading look at them both in an attempt to diffuse the situation. "We're finally all together again, can we just have one night where we all get along?”

Loki shifted in her seat but didn't look up, fork frozen over a piece of turkey. "I'm sorry," she muttered, dropping the fork and excusing herself, leaving the rest of them to stare at each other in silence. Thor couldn’t blame her. If he could get out of spending the rest of the evening fielding questions he had inadequate answers to, he would too.

It wasn't until the dishes were washed and drying and Thor had politely sat through the end of some Judy Garland film Frigga loved that Loki finally made another appearance. She flopped down on the couch next to Thor as though nothing had happened and Thor saw a smile sneak onto their mum’s lips for the first time all evening. It still wasn't exactly easy between them, but if Loki was making an effort, he could as well.

They found themselves inching closer as the night wore on. Thor wasn't sure if it was even conscious on Loki's part. Either way, he knew better than to make a point of it. The last thing he wanted was to push her further away. It was hard to resist testing the water though, just a little. Wordlessly, he found himself leaning over, letting their shoulders brush together, their thighs touch. If he pretended he was focused on whatever was happening on the TV instead of the tension between them, he could play it off like it wasn’t a big deal. Which it wasn’t. 

This year’s Christmas movie was The Grinch, the same as last year. And the year before that. They must have seen it tens of times growing up. To Thor’s relief, Loki hadn't stormed off yet. If anything, she relaxed into him as the movie went on, the guarded look on her face giving way to one of genuine enjoyment.

“Do you remember when we used to stay up all night?” Loki asked suddenly, turning to face him. Frigga had left, leaving the two of them alone together for the first time all week.

“You were too excited to sleep,” Thor chuckled. “Of course I do.” 

Loki was smiling back at him. “You know I figured out where they hid our presents by the time I was four.”

“Naturally.” 

She snorted. “Didn’t you wonder why I was still excited then? Or was I just that good of an actor?” 

“I assumed it was part of the ploy.” 

Loki stared at him, her eyebrow twitching ever so slightly. Thor was suddenly very aware of how close her face was to his.

“That and you wanted to spend as much time with your awesome big brother as possible. I mean, who wouldn’t?”

Thor didn’t have time to react before the pillow hit his face. His eyes lit up, laughing as he shoved it back at her, holding her arms down as she tried to kick him away. Without thinking, he wrapped his arms around her and pulled her into a hug before she could respond, the pillow still wedged between them. Loki was giggling too. Thor could feel her whole body shaking and after all this time, it was the most wonderful sound he’d ever heard. He vowed to make sure he heard it again before they had to leave. 

The laughter died off as the two of them pulled away Loki tensed, sheepishly, as though she’d only just realised she was having fun. Thor half expected expected her to leave again but after a second she shuffled down to lay her head on his shoulder. His stomach flipped at this small victory and he realised with a start that he didn’t want this moment to end. Before he could explore that thought further, it was interrupted by their mum returning with hot chocolate. There must have been more whipped cream, marshmallows and sprinkles than actual hot chocolate. Perfect.

“I’m having an early night kids,” she told them, wishing them good night and bending over to give them both a kiss. “Enjoy.” It was selfish and irrational, Thor knew, but he was glad he had her to himself again. 

Frigga had left them spoons but for some reason Loki decided to drag her finger through the spiral of cream instead, wrapping her lips around it and sucking it clean. Thor choked on his mouthful at the sight of it, feeling the colour rise to his cheeks. But Loki didn’t seem to notice. She closed her eyes as she took a sip, tongue darting out to catch the circle it left around her mouth. Thor didn’t realise he was staring until she shoved him.

“What?”

“Nothing,” he laughed, feeling his stomach drop. There was no easy way to tell your sister you wanted to lean over and kiss her. And there was no denying that now. It wasn’t enough to get to spend time with her again. He wanted to touch her in ways that were distinctively not brotherly - to know what her lips tasted like, how they felt against his, what sounds she might make when he slipped his tongue in -

“What? Do I have some on my face?” She screwed her nose up, reaching for her phone to check, not waiting for his answer.

Thor managed another laugh as she fussed but it felt hollow. He’d finally gotten what he wanted - the only thing getting in the way of their relationship now was his awful desire to ruin it completely. Loki elbowed him as she laid back, allowing Thor to hold her again. She looked cagey once more, hesitant, as though she could tell something had changed between them in that moment.

Their mugs were long finished by the time the credits started rolling, piano notes filling the room as the sound of Faith Hill rang out. Thor quietly snorted at the cheesy lyrics. They’d both changed so much over the past year but despite all that, she was still his little sister. The same kid he'd played house with, Thor dressed up in their father's clothes and stumbling over himself in shoes that were far too big for him as he bent down to kiss his ‘wife’. That memory should definitely have put a stop to the fluttering in his chest, but to his horror, it only made it worse. _She was his little sister_. Christ.

Thor was in no rush to get up and neither was Loki. He was curved around her now, balancing precariously close to the edge of the couch. Somehow, they managed to fit together. It seemed every part of his body was touching her - his feet wrapped around her ankles, stomach pressed up against her back, arm reaching around to make sure she didn't fall off. And if, at some point, he'd reached over to pull the throw over them and tuck his head into her neck, it was just because it was cold, really. 

Thor was still absentmindedly tracing circles along her side as the song faded out. Their parents must have gone to bed by now. It would be so easy to fall asleep like this. He didn’t realise his hand had moved higher until he felt it brush over Loki nipple. His eyes flew open. _This wasn't appropriate anymore._ He wasn't sure if it had ever been totally appropriate, but it sure as hell wasn't now. He'd accidentally groped his sister. Awkward. The way Loki’s breath hitched and a little noise escaped as she exhaled? Infinitely more awkward. 

Thor’s hand jerked away. Loki hadn’t leapt up and ran away yet and that was something at least. As they lay there, frozen, Thor felt the gulf between them widen again. In the background, the commercials droned on, but all he could focus on was their shaky breathing; their hearts thudding frantically. The longer this moment dragged on the harder it would be to laugh off.

Loki finally broke the silence. “Thor?” Her voice wavered.

“Yeah?” He replied, softly. It was a question.

“I liked that.”

“Oh.”

“Yeah.”

“I did too.”

They fell into silence again, both waiting for the other to do something with this information. Thor wasn’t sure what was running through Loki’s head right now. He had to be certain. “Do you want me to do it again?”

She hummed in response, nodding against him. _Oh thank god_.

Thor could think about what this meant later. Heart pumping and wide awake now, his fingers trailed higher again, cupping her breast. She let out another little sound, leaning into him. He felt himself getting hard as his fingers rolled over her nipple consciously now. Shifting slightly so she could reach back and grasp his thigh, Loki squeezed him every time the attention managed to send tremors down her body. Thor’s fingers danced down her torso, tentatively hooking them under the edge of her shirt.

“Is - is this okay?” he asked, rubbing her arm reassuringly.

“More than okay,” came Loki’s shaky reply.

It was the permission he needed. Her breast fit easily in his hand as he gave it a tentative squeeze, appreciating the feeling of her warm skin against his. Loki was leaning into the pillow in an attempt to stifle her moans and Thor _really_ hoped their parents were asleep by now.

As he rolled her over so she was underneath him, Thor felt her against his thigh for the first time, already half hard. Loki met his eyes as he brushed her cock, mouth open and face flushed. Leaning down, close enough to feel her breath on his lips, Thor paused. He was getting the order all wrong, but he supposed there wasn’t a guideline to getting to second base with your sister. It was Loki who closed the distance, kissing him softly, encouragingly. It was so much more than he had imagined.

Licking his lips as he broke away, Thor kissed a trail down her neck, pulling her shirt further up as he went. Loki took the cue to take it off, allowing Thor to latch onto her nipple and suck, leaving it red and puffy and glistening with spit when he pulled away. She was positively shaking now, her hands gripping his shoulders tight enough that Thor was sure he’d have marks tomorrow.

“Do you think you could come just from this?” he breathed against her chest.

Loki whimpered, bucking her hips up. “Maybe,” she admitted. She was already panting, breathless.

Thor, taking that as a challenge, lightly circled her nipple with his tongue again, leaving her trembling beneath him.

“You’re so gorgeous like this, sister. So cute,” Thor admitted, feeling the truth in his words in how his clit cried out for attention. But this was about Loki now, that could wait. His tongue gently flicked her other nipple before giving it the same attention, rubbing it between his lips and letting his teeth graze her slightly as he pulled off. 

Loki had long since given up on staying quiet, her hips thrusting up into him. “Thor,” she moaned. “Thor, I’m close, please.”

It was Thor who bit his lip now, his own orgasm also embarrassingly close just from hearing how eager she was for him. Unable to help himself, he begun to rock into Loki’s leg, rubbing himself off against her. Able to feel exactly how wet she was making him now, Thor continued to mouth at his sister’s chest, pushing the small mounds of her breasts together.

Loki raised her thigh to meet him as he rode it. “Come for me, brother. I want to make you feel good too.”

Thor groaned as her voice tipped him over the edge, his face pressed up against her chest. As soon as he could, he renewed his efforts, reaching up to pinch the nipple not surrounded by the warm heat of his mouth. Moving his leg at the same time, he gave her cock the slightest amount of pressure. That was all she needed. Thor felt her body tense as she choked out a wordless gasp and twitched against him, wetness spreading across her pants. Another thing they’d have to deal with in the morning. For now, he had his sister snuggled into him, pressing sleepy kisses to his neck.

And if their parents walked in on them like this in the morning, well, it was just like old times, right?

**Author's Note:**

> alternative title: Grinch n chill


End file.
